http: replace startsWith with strict equality

PR-URL: https://github.com/nodejs/node/pull/59394
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Zeyu "Alex" Yang <himself65@outlook.com>
Reviewed-By: Jordan Harband <ljharb@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

lib/internal/http.js

@@ -156,7 +156,7 @@ class ProxyConfig {
       if (entry === host || entry === hostWithPort) return false;  // Matching host and host:port
 
       // Follow curl's behavior: strip leading dot before matching suffixes.
-      if (entry.startsWith('.')) {
+      if (entry[0] === '.') {
         const suffix = entry.substring(1);
         if (host.endsWith(suffix)) return false;
       }